Originally Posted by darkroomsource
I haven't been able to do instrument approaches in Oregon without an IFR plan.
Not sure where you were flying or exactly what your experience was, but this is by no means typical. There are dozens of airports in Oregon with instrument approaches which have neither a tower nor approach control, at which it would be perfectly legal to go out and practice instrument approaches to your hearts content in Visual Meteorological Conditions, under VFR. No IFR clearance nor contact with ATC required. (although talking to the overlying ARTCC may be a good idea for traffic avoidance)
Those aren't the only situations where that would be legal, either. As Westhawk pointed out earlier, it would also be perfect legal to do practice approaches under VFR in VMC at an airport with a tower and approach control. ATC may have a very strong *preference* that you be on an IFR clearance, and for their reasons they may not approve you to do that VFR, but that doesn't mean that it's a legal requirement to be on an IFR clearance.
Originally Posted by darkroomsource
And once I've filed an IFR plan, I'm on instrument flight rules.
Well no, not to split hairs (OK, I'm splitting hairs) you're not under instrument flight rules until you accept an IFR clearance.